Two-stage fluid pumps



June 14,1960 F. G. MATTos 2,940,397

Two-STAGE FLUID PUMPS Filed April 26, 1956 3 Sheets-Sheet l lNveNroQ FRANK 6.01/7 77' 05 BY MM50@ M" ajaovd Armani-Yrs June 14, 1960 F. G. MATTos 2,940,397

TWO-STAGE FLUID PUMPS Filed April 26, 1956 3 Sheets-Sheet 2 FRANK G, M T705 June 14, 1960 F. G. MATTos Two-STAGE FLUID PUMPS 3 Sheets-Sheet 5 Filed April 26, 1956 INveNTcR FRANK G. MA1-ros BY v- A-rroaNEYS Unite States Patent TWO-STAGE FLUID PUR/IPS Frank Guy Mattes, Hayes, Engiand, assigner, by mesne assignments, to Fairey Aviation Limited, Hayes, England, a company of Great Britain Filed Apr. 26, 1956, Ser. No. 530,822

Claims priority, appiication Great Britain Apr. 26, 1955 Claims. (Cl. 10S-438) The invention relates to two-stage fluid pumps and one object is to provide an eti'icient high speed pump capable of meeting changes in demand.

According to the present invention, a multi-cylinder vaableangle swashplate fluid pump comprises a casing, a rotatable driving shaft extending through the casing, a pair of opposed swashplates mounted in spaced alignment on the driving shaft for rotation therewith within the casing, each of the swashplates `being pivoted about a tilting axis transverse to the shaft axis, cylinder means xedly mounted within the casing and affording two groups of pumping plungers of which each group is circumferentially disposed around the shaft axis in operative engagement with the face of one of the swashplates 'for actuation thereby, and angle-adjusting mechanism operable to vary the angle of tilt of both the swashplates simultaneously by tilting them in opposite directions about their transverse tilting axes, the said angle-adjusting mechanism comprising a hydraulic jack mounted on the driving shaft for rotation 'bodily with the swashplates and engaged between opposed peripheral portions of the two swashplates to apply oppositely directed tilting forces thereto, the jack being supplied with pressure fluid rom a non-rotary source. The said means may include a pilot valve element within a shaft carrying the swashplate and acted on by the output pressure to move in response to changes in the output-pressure to admit output pressure to an actuator rotatable with Ythe swashplates, for varying the swashplate angle, for example by means of a cam acting on the swashplates. i

Preferably the pivot axis of the swashplateV is oliset from theV centre of Arotation of the plate away from the surface where the cam acts on the plate in order that a resultant torque about the hinge axis' shall tend always to keep the swashplate against the cam.

The invention may be carried into practice in various dierent ways and one specific embodiment will be described by way of example with reference to the accom'- panying drawings, of which:

Figure l is a longitudinal cross-section through av twostage uid pump intended to run at about 6000 rpm.,

Figure 2 is a diagrammatic View similar to Figure 1 and showing the route followed by the uid, and

Figure 3- is a perspective View, partly broken away, of the hydraulic actuator vfor varying the angle of the swashplates in the second stage, and

Figure 4 is al sectional plan of the hydraulic actuator of Figure 3. v

The pump has a non-positive centrifugal first stage constituted by an impeller 11 mounted on lthe main shaft 112 which is driven from the left hand end as seen in Figure l. 'lf-he second stage is constituted by a pair of swashplates 13 and 14 mounted to rotate with the shaft 12 and each' associated with seven reciprocators arranged around' th'e shaft 12 adjacent the outer surface of the plate. As can best be seen in Figure 2, the swashplates 13 and 14 are pivotally mounted about a transverse axis 15 a little to one side of the axis of the shaft 12 so that they can be moved between a position in which they are perpendicular to the axis of the shaft 12 and a position in which they make a smaller angle with the axis of the shaft. In Figures l and 2 the swashplates are shown in an intermediate position.

Each swashplate reciprocator consists of axed cylinder 21 iitted in the casing 22 Iot the pump and a piston 23 constituted by a slidable Vtelescoping tube which has a hollow .henri-spherical cup 25 interposed between a corresponding seat in the closed end of the piston 23 and the surface of the swashplate. The ends of the piston and the cup 25 are bored to allow fluid pressure in the cylinder 21 to act against the iface of the swashplate and lelect a pressure balance. rIlhe cup 25 is maintained in contact with the swashplate, and the piston 23 in contact With the cup by means of a spring 27 surrounding the piston and interposed between a fixed part and an annular external flange 24 at the closed end of the piston. A pin 26 serves to prevent the cup 25 from moving more than a short distance away from its seat in any circumstances. Alternatively a positive means of connecting the piston to the swashplate may be used particularly at high speeds. V

As it is well understood, the swashplate stage operates as the swashplates rotate to produce a reciprocating or pumping action of the pistons 23 in the cylinders 21. The stroke varies from zero when the plate is perpendicular to the axis of the shaft 12 to a maximum when the plate is inclined at the minimum angle to the shaft axis.

Fluid is drawn into the pump through an opening 31 in the right hand end on the axis of the pump which leads to the input of the impeller 11 aroundV an ogival boss 32 held in position Within theopening4 31 byrthree radial ribs 33. In the Ifirst stage the iuid is raised to a pressure of about 90 lbs. per square inch, and it travels by Way of a passage 34 to a swashplate chamber 35 which surrounds the shaft 12. Equally circumferen# tially spaced in each `end wall of the swashplate chamber 35 are seven valves 36 leading each to one of the cylinders 21 through a circumferential passage. Y

Each valve 36 is a non-return valve having an open@ ing normally closed bya diaphragm 37 under the action of a compression spring 38. On the suction stroke' of each piston 23 the pressure drop across the valve 36 allows fluid to flow yfrom the swashpla'te' chamber 35 to the inlet 39 of the corresponding cylinder 21.

The outlet from the cylinder 21 is controlled. by a' similar non-return valve i2 which is biassed Iby a spring 43 to be closed as long as' the pressure on its outlet side is greater than the pressure in the cylinder 21. 'Iihus after iluid' has been introduced into the cylinder 21, on the compression stroke of thepiston 23 li-uidv is raised to a pressure `of about 4000 lbs. per square inch at which the valve 42 opens to admit high pressure fluid to a passage 44 which leads by way of an annular chamber 45 to a radial outlet passage 46. The outlets from the seven cylinders associated with the left hand swashplate 14 lead directly to the outlet 46 but those from the seven cylinders associated with the right hand' s'wash'- plate 13 lead to the outlet 46 by way of a' radial' passage 47 and a longitudinal passage 48.

The machine for controlling the angle of: the sw'ashplates is yoperated hydraulically through the shaft. Y Thus the shaft 12 runs in ball bearings 51 and 52 held in housings formed in the casing l22 and at its' rightV hand en'd A 219402391 p. n "um I" H mi Y; ft sisplinedtoan auxiliV f' ary-shaftSS which inuturn ispsplined y 'effect is achieved when the pump is stationary by means in the casing 22. 'Ihe sleeve 54 has a central hole 55 which leads to a longitudinal bore 56 in the auxiliary to a sleeve 54 ymounted to rotate in ball lbearin'gsfSS heldY *Y shaft 54 and this in turn lleads to a chamber 57 in the 5 Y end 'oftheimainrshaft.12`intowhieli isscrewed -a sleevej *Y From the'radial passage 47 asmall passage 65'leads by way ofa radial passage 66 to a-chamber 67 formedV in the .ogival boss 32 positionedivithin the inlet to Ythe impeller 11 so that uidiat Substantially the outlet pressureV from Vthe/second stageY is 'admitted throughVl the hole 5.5 and Vthe jbore 56 intoV theV chamber 57Y within` the' ,shan .12. Y

:Y The. right hand end of the sleeve Stlris closedby Ya. bung -71 screwedV intoit while the sleeve Y58.itself is held in positioneby being screwed into a threaded countercircumferential discontinuities .providing longitudinal passages arrangedraroundthe sleeve 58 to admit'fluid from Y the chamber-57 tojarcentral longitudinal bore 74 inthe pilot valveelement V59 yby way of a fluid `passage'75 formed inthe sleeve 58 Vandya'circumferential recess 56 in demandvon the pump, by Vmoving, thepilotfvalve eleof a plunger 104 which can slide in a radial socket 105 formed in the shaft ,12, and which is urged outwards by means of a compression spring 106 into contactwith ears 107 :formed on the two swash platesV so that the spring always tends Yto move theplunger 104 in the direction toA move the two ears. 107k appart and thus hold the lugs 102 in contact with'the caml V101. j Y

It will be seenythat anyvariation'in'the outlet press ure fromV the second/stage, for example due to a change mentY 59 operates the hydraulicv actuator 83'to turnv the cam 101 and thus to vary lthe angles of the swashplates 13 and 14 tochange the quantity of *liuid pumped per cycle: in the sense to compensate for the change in pressum'. ,Y Y .j

By virtue ofthe first stage 11 being a non-positive Y y stage, li.e.-, a stage which does not pump a specified quann bore 72 =formed within the shaft 12?..` VThe thread has 'n nearvrth'e right Ahand end of the element 59. The net effect ofthe iiuidrin this bore 74V is .torbalance the thrust of thespring 62vwhen the outlet pressure is'at the de- 83 to be described in -rnore detail below.' These ports' I 8,1 and 82 are normally/.closed by lands'84y and 85 formed on thepilot valve element `59 and it can be seen Y Y that if the outlet pressure vitrom the swashplate second stage increases `or decreases the pilot valve element-59 willbe moved to the left orto the lright to admit pressure liuid to one or other of 'the ports 81 and 82.` t Y The actuator'83 is shown tdiagrammaticallyin Figures 3 Vand ai and'v comprises a cylindrical'socket 91ffor1ned integrally wit the shaft 12andY provided with two dia-`V V'Jrietrjically opposed inwardlyprojecting walls 92 between tity offliuid per cycle but Vwhose quantity pumpaidependsrupon the `demand,"'iio lmeans isrequi'red to compensate for changes in the demand fromthe second stage while the centrifugal Ystagevzrcan' operate at high speed and therefore fairly eliiciently. Since mostofthe power Vdeveloped in the second stage, the relatively low eflciency` of the first stage Vis'not very noticeable. Oontrolledbleed orificescan be arranged'to dissipate heat losses in-t-he'first stage when itis not pumping flid.

lV Finally it is pointed out that fby'mountingl twoswashplates back-to-.back 'the resultant axial lead onY the shaft t is .balanced While since't-heY means for adjusting the swashplate angle vin laccordance with. the outlet pres'- sure is contained within the shaft :12, no thrust bearing is requi-redas would bet-he caseif the swa'shplate angle wereV adjusted by a non-rotating member.V 'Ilhe characteristic ofthe pump at 6000- rpm. is such that l8gallons can be pumped per minute with a 4 swashplateV angle, while at an {angle'ofr' 21/2, this rate of; pumping Yis approximately` halved. YThus a Zsmall change in the angle can compensate forquite a large change in demand. i .j What'I claim as my inventionra'nd desire to secure by Letters Patent is:

. Y l. A multicylinderlvariabledangle' swashplate iuid whose inner ends is positioned theshaft 93 of a butter- Y fly 'pistonpwhich can turn in journals lformed in platens 97Vand V98 .at either end of the socket 91 as shown in Figurefl. The'wingsj94'and 95 of the butterliy are positioned lone in1each of the `two sector-shaped Vchambers 99zand4100V into which the interior of the socket 9,1 ris divided by the 'walls '92. 'Ihe Vtwo ports 8l andY 82 lead into the chamber 100 as seen in Figure 4,' oneY on either side ofthe piston wing 95, and the shaft 93 has Ytwo non-intersecting diametrical bores 9'6, eachY of which servesV toltransmit fluid from one chamber onone side of the wing'95 to the corresponding chamber'on the voppositefside of` the wing 94 so that it acts dilerentially on both wings 94 and 95 and can rotate the piston. 'Ilhe VYupper end ofthe shaft 93 has secured to it an oval and'in consequence regulate the quantity of fluid delivered-bytheiswashplate stage. 1. y As has'beenalready described thefswashp'lates pivot 1 about an axis 15 displaced on theothersideo'f theY axis ofthe shaft 12 from the'cam101 vand this ensures'that during'operation those cyli`nde'rs21V which are AonrtiheirV compression strokeihave'a net torque tendingtourge Y the swasliplates intocontact'with thecam 101 K The same pump which comprises a casing, a'rotatablel driving shaft extending through lthe casing, a pairrof opposed swash` plates mounted in spaced alignment on the driving shaft forrotation therewith within'the casing, eachrof the Vsvwashplate's being pivoted about a 'tilting axis transverse to the 'shaft axis, Vcylinder-means xedly mounted within the casing and affording two groups of pumping plungers of which eachgroup is circumferentially disposed around f the] shaft axis in operative engagement with the face of one'of the swashplates for actuation thereby, and angleadjustng mechanism operable to vary the angle of tilt of both the swashplates simultaneously by tilting them in opposite directions about their vtransverse tilting axes, the said angle-adjusting mechanismcomprising a hydraulic jack mounted on the driving shaft for lrotation bodily with the swashplates and engaged between opposed peripheral portionsof the two swashplatesl to apply oppositely directed'tilting forces thereto, 4the jack being supplied with pressure fluid 'from a non-rotary source. Y

2. A .pump as claimed in claim 1 including a servo valve disposed within a bore in the driving shaft and in. lluid communication with said jack and being arranged to control the operation 'of the hydrauliciack'.

3L'A pump as claimed in claim 2 in which the hydraulic jack comprises a rotary jack spindle driven by a hydraulic Vmotor and a'cam'mounted on the jack spindle, the cam` having duplicate camsurfaces respectively Vin camming "engagement Ywith the said opposed peripheral portions of the two swashplates. 1 .Y f

'Y 14.. A pumpas claimed in claim 3 in which thems- `verse;` tiltingjaxis zofY each swashplate Vis ofi-set from the nomas? axis of the driving shaft on the opposite side thereof from the said peripheral portions of the swashplates engaged by the cam.

5. A pump as claimed in claim 3 in which the hydraulic jack comprises a jack cylinder carried by the driving shaft and rotatable therewith, the 'axis of the cylinder being at right angles to that of the driving shaft, a vane-type rotary piston mounted on the jack spindle within the casing, and inlet means controlled by the servo valve and arranged to admit hydraulic pressure uid into the jack cylinder diierentially on opposite sides of the piston to rotate it together with the jack spindle and thereby to rotate the cam.

References Cited in the file of this patent UNITED STATES PATENTS Linthicum July 2l, 1936 Aspelin etal Dec. 13, 1955 Smith Mar. 13, 1956 Wemhoner Apr. 10, 1956 Cardillo et al Nov. 6, 1956 FOREIGN PATENTS Great Britain July 10, 1947 France Nov. 4, 1953 

